YIJOM-3735; No of Pages 7
Int. J. Oral Maxillofac. Surg. 2017; xxx: xxx–xxx http://dx.doi.org/10.1016/j.ijom.2017.06.019, available online at http://www.sciencedirect.com
Clinical Paper Orthognathic Surgery
Condylar positions before and after bilateral mandibular distraction osteogenesis in children with Pierre Robin sequence
J. Liu, Y. Chen, F. Li, W. Wu, J. Hao, D. Luo, H. Wang Department of Oral and Maxillofacial Surgery, Stomatological Centre, Guangzhou Women and Children’s Medical Centre, Guangzhou, China
J. Liu, Y. Chen, F. Li, W. Wu, J. Hao, D. Luo, H. Wang: Condylar positions before and after bilateral mandibular distraction osteogenesis in children with Pierre Robin sequence. Int. J. Oral Maxillofac. Surg. 2017; xxx: xxx–xxx. ã 2017 Published by Elsevier Ltd on behalf of International Association of Oral and Maxillofacial Surgeons. Abstract. This study aimed to analyze the changes in mandibular morphology after bilateral mandibular distraction osteogenesis (BMDO) in children with Pierre Robin sequence. The positions of the condyles were analyzed in reconstructed threedimensional craniomaxillofacial images obtained for 18 children before and 8–12 weeks after BMDO. Differences between pre- and postoperative parameters were assessed using paired t-tests. After surgery, a significant decrease in superior joint space was detected (P < 0.05), but no change in anterior joint space or posterior joint space was observed. The ratio of the distance between gonia and distance between condylion points (GoL–GoR/CoL–CoR) (P < 0.001) and the distances between the condyle and midsagittal plane (P < 0.001) increased after surgery, while the condylar horizontal angle decreased (P < 0.05). No change in condylar vertical angle was noted. After BMDO, the condyle displayed an outward and upward shift, as well as outward rotation along the proximal segment. The mandible body exhibited forward movement with a more significant opening range. These changes were consistent with the extent of the newly formed bone tissue and the improvement in coordination and appearance of the children’s facial structures. The long-term effects of changes in condylar position on the development of the maxillofacial structures needs to be studied further.
Pierre Robin sequence (PRS) is a rare congenital mandibular abnormality with a reported prevalence ranging between 1/8500 and 1/20,0001. PRS is character0901-5027/000001+07
ized by micrognathia and glossoptosis, with or without cleft palate. The deformities may result in airway obstruction in the neonate, often accompanied by cyanosis
Key words: Pierre Robin sequence; condyle; joint space; bilateral mandibular distraction osteogenesis. Accepted for publication
and retraction of the intercostal space and upper fossa during inspiration. There may be serious clinical consequences for children with multiple PRS malforma-
ã 2017 Published by Elsevier Ltd on behalf of International Association of Oral and Maxillofacial Surgeons.
Please cite this article in press as: Liu J, et al. Condylar positions before and after bilateral mandibular distraction osteogenesis in children with Pierre Robin sequence, Int J Oral Maxillofac Surg (2017), http://dx.doi.org/10.1016/j.ijom.2017.06.019
YIJOM-3735; No of Pages 7
2
Liu et al.
tions, and the mortality rate is estimated to be up to 26%. Also the movement of the epiglottis may be restricted in children with PRS, resulting in chronic malnutrition1. Prone positioning is the first-line noninvasive management of PRS. In the case of persistent airway obstruction, a surgical intervention is required, such as tongue– lip adhesion, tracheotomy, or mandibular distraction osteogenesis (MDO)2. Over the last two decades, distraction osteogenesis has been tested for the correction of temporomandibular joint (TMJ) deformities in animal models as well as in the clinical setting3,4. Bilateral mandibular distraction osteogenesis (BMDO) improves glossoptosis by extending the mandible, thus clearing the airway. This has become the primary choice for the treatment of patients with severe mandibular retrognathia5. It is generally suggested that BMDO is performed at an early stage to improve breathing and nutrition in a timely manner, and therefore to improve quality of life. In BMDO treatment, truncation and facilitated forward movement of the mandible bone segment may cause a shift in position of the teeth, jaws, skull, and/or facial structures. Changes in mandibular morphology and position may affect the fine anatomical structures and function of the TMJ6. Furthermore, the bone composition of infants is more flexible and will adapt during reconstruction of the facial structures. Therefore significant changes in the relative positions of the temporomandibular articulation and mandible may occur during the postoperative period after BMDO treatment. Most perioperative studies have concentrated on changes in the mandible structure from the pathological perspective, with little attention paid to changes in the intact mandible morphology and position during the developmental stages after BMDO, especially the long-term impact on craniofacial development. In this study, the facial structures of patients before and after BMDO treatment were analyzed using reconstructed three-dimensional (3D) craniofacial computed tomography (CT) images. The mandibular morphology was evaluated with quantitative parameters reflecting the relative positions of the condyles. The potential impact of BMDO on the development of the mandibular structures is discussed.
and Children’s Medical Centre. Consecutive patients who underwent BMDO for the treatment of PRS in the Department of Oral and Maxillofacial Surgery of Guangzhou Women and Children’s Medical Centre from May 2013 to October 2015 were included. PRS was diagnosed according to the following criteria: (1) micrognathia and glossoptosis with breathing/swallowing difficulties, defined as the need to maintain a lateral or prone position, or the requirement of assisted mechanical ventilation for respiration, and/or need for tube feeding; (2) reconstructed 3D maxillofacial and laryngeal airway CT images confirming significant tongue falling and upper airway stenosis, with the narrowest position detected between the rear end of the tongue and the hyoid bone. Patients were included in the study if they fulfilled the necessary eligibility criteria, as outlined below.
Eligibility criteria
The following inclusion criteria were applied: confirmed diagnosis of PRS; no previous surgical treatment such as tongue–lip adhesion; preoperative examination showing a normal bilateral TMJ structure with a normal degree of mouth opening; patient able to tolerate surgery under general anaesthesia; the availability of long-term follow-up records (minimum 2 years). Exclusion criteria were the presence of any other severe congenital deformity, metabolic disease, chromosomal disorder,
or dystonia, or the presence of a breathing or eating disorder of unknown cause not directly related to PRS.
Surgical procedure
All patients underwent BMDO under general anaesthesia. A parallel incision was made about 1.5 cm from the inferior border of the mandible close to the mandibular angle. The osteotomy line was designed according to the preoperative 3D CT findings. A ‘walking-stick’ shaped osteotomy line passing through the mandibular angle was utilized to avoid the tooth bud and condylar neck. After a rest period of 48–72 h, mandibular distraction was performed at a speed of 1.2 mm/day. The positioning of the distractors is shown in Fig. 1. Distraction was performed until the upper and lower jaws were symmetrically aligned or a slight underbite was achieved. The maximum traction distance was limited to 1.5 cm. Imaging and analysis of the 3D craniomaxillofacial structures
Three-dimensional maxillofacial CT was performed before and at 8–12 weeks after surgery using a Philips Brilliance CT64 scanner with settings of 120 kV, 130 mA, and 0.9-mm layer thickness. Structure reconstruction was then accomplished using Mimics version 10.0 software (Materialise, NV, Leuven, Belgium) to acquire coronal, sagittal, and axial views.
Methods Setting and patients
This retrospective study was approved by the Ethics Committee of Guangzhou Women
Fig. 1. Positioning of the distractors in this study.
Please cite this article in press as: Liu J, et al. Condylar positions before and after bilateral mandibular distraction osteogenesis in children with Pierre Robin sequence, Int J Oral Maxillofac Surg (2017), http://dx.doi.org/10.1016/j.ijom.2017.06.019
YIJOM-3735; No of Pages 7
Condylar positions before and after BMDO in PRS For the analysis of the craniomaxillofacial structures, morphological parameters were measured, including spatial distances and ratios and relative positions (angles) between anatomical structures, as described below. The superior joint space (SS), anterior joint space (AS), and posterior joint space (PS) were measured as reported previous-
ly7: line ‘a’ was drawn perpendicular to the horizontal plane through the top of the condyle; line ‘b’, which was at 45 degrees to the horizontal plane, was drawn through the narrowest position of the anterior joint space; line ‘c’ was drawn perpendicular to line ‘b’ through the intersection of ‘a’ and ‘b’. The segment lengths of lines ‘a’, ‘b’, and ‘c’, which were located in the joint
3
space, were measured as SS, AS, and PS, respectively, as shown in Fig. 2A. The condylar horizontal angle (a) was measured on the axial image. The angle between the horizontal plane and a line drawn through the inside and outside poles along the long axis was measured as the condylar horizontal angle (a), as shown in Fig. 2B.
Fig. 2. Measurement of the morphological parameters of the craniomaxillofacial structures. (A) Joint spaces: line ‘a’ was drawn perpendicular to the horizontal plane through the top of the condyle; line ‘b’, which was at 45 degrees to the horizontal plane, was drawn through the narrowest position of the anterior joint space; line ‘c’ was drawn perpendicular to line ‘b’ through the intersection of ‘a’ and ‘b’. The segment lengths of lines ‘a’, ‘b’, and ‘c’, which were located in the joint space, were measured as SS, AS, and PS, respectively. (B) Condylar horizontal angle (a): the angle was measured on the axial image; this was the angle between the horizontal plane and a line drawn through the inside and outside poles along the long axis of the condyle. (C) Condylar vertical angle (b): the angle was measured on the coronal image; this was the angle between the sagittal midline and a line drawn through the inside and outside poles along the long axis of the condyle. (D) Distance between the condyle and midsagittal plane (r): this distance was measured on axial images as the distance between the outside pole of the condyle and the midsagittal plane. (E) GoLGoR/CoL-CoR ratio: the distance between gonia on the two sides (GoL-GoR) and the distance between condylion points on the two sides (CoLCoR) were measured; the ratio between these distances was used to evaluate the degree of opening of the mandibular arch relative to positioning between the condyle and mandibular body.
Please cite this article in press as: Liu J, et al. Condylar positions before and after bilateral mandibular distraction osteogenesis in children with Pierre Robin sequence, Int J Oral Maxillofac Surg (2017), http://dx.doi.org/10.1016/j.ijom.2017.06.019
YIJOM-3735; No of Pages 7
4
Liu et al.
Table 1. Characteristics of the study subjects and mandible extension results.
Patient ID number
Sex
Age (days)
Weight (kg)
Requirement for assisted mechanical ventilation
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
M F M F M F M F M M F M F M F F F M
69 107 244 110 52 24 31 50 153 213 160 48 93 213 17 42 17 87
3.1 3.5 8.3 3.2 4.4 2.9 3.2 3.4 4.6 6.4 4.5 4.4 4.1 6 3.1 2.6 3 5
N N N N N N Y N N N N N N Y N N N N
Requirement for auxiliary feeding tube
Postoperative extension of the mandible (left/right) (mm)
Y N N Y Y Y Y N Y N N N N Y Y Y Y Y
12/12 12/12 10/10 8/8 13.6/18.4 15/20 11.5/10 1.5/15 15/15 13.5/10 11.5/2 8/1 12.5/12.5 13.5/3.5 11.5/10 15/12.5 13.5/15 12.5/8.5
F, female; M, male; Y, yes; N, no.
The condylar vertical angle (b) was measured on the coronal image. The angle between the sagittal midline and a line drawn through the inside and outside poles along the long axis of the condyle was measured as the condylar vertical angle (b), as shown in Fig. 2C. The distance between the condyle and midsagittal plane (r) was measured on the axial image. This was the distance between the outside pole of the condyle and the midsagittal plane, as shown in Fig. 2D. The distances between the gonia on the two sides (GoL–GoR) and the distance between the condylion points on the two sides (CoL–CoR) were measured, as shown in Fig. 2E. The ratio between these two distances (GoL–GoR/CoL–CoR ratio) was used to evaluate the degree of opening of the mandibular arch relative to positioning between the condyle and mandibular body.
Statistical analysis
Parameters measured were expressed as the mean standard deviation. Comparisons between the pre- and postoperative data were performed using the paired ttest. A P-value of 0.05), indicating that there was no significant movement in the anterior or posterior direction of the proximal segment of the mandible. Significant increases in r values were observed after surgery (P < 0.001), indicating an outward movement of the condyles. The GoL–GoR/CoL–CoR ratio was increased postoperatively compared to the value before surgery (P < 0.001), indicating an increase in mandibular opening and a widening of the mandibular arch. The angle a was increased on both sides (both P < 0.05) after the completion of distraction, while no significant change in angle
Table 2. Comparison of morphological parameters before and after surgery. N = 18
Preoperative
Postoperative
SS-L (mm)* SS-R (mm)* AS-L (mm) AS-R (mm) PS-L (mm) PS-R (mm) a-L ( )* a-R ( )* b-L ( ) b-R ( ) r-L (mm)* r-R (mm)* GoL–GoR/CoL–CoR*
2.12 0.43 2.20 0.57 1.90 0.46 1.92 0.41 3.35 0.78 3.15 0.73 24.94 6.60 26.07 8.28 78.12 8.36 76.75 10.03 34.95 2.63 34.88 2.50 0.75 0.05
1.90 0.40 1.91 0.38 2.00 0.52 2.04 0.47 3.19 0.71 3.33 0.88 20.46 8.97 21.04 9.01 78.03 5.96 76.61 7.26 39.40 2.46 40.09 3.01 0.77 0.06
t
P-value 2.779 2.567 0.845 0.888 0.681 0.780 3.324 3.582 0.043 0.050 5.972 8.744 4.986
L, left; R, right; SS, superior joint space; AS, anterior joint space; PS, posterior joint space; a, condylar horizontal angle; angle; r, distance between condyle and midsagittal plane; Go, gonion; Co, condylion. * Statistically significant difference detected between pre- and postoperative measurements.
0.004 0.009 0.409 0.387 0.505 0.446 0.020 0.014 0.966 0.961
Int. J. Oral Maxillofac. Surg. 2017; xxx: xxx–xxx http://dx.doi.org/10.1016/j.ijom.2017.06.019, available online at http://www.sciencedirect.com
Clinical Paper Orthognathic Surgery
Condylar positions before and after bilateral mandibular distraction osteogenesis in children with Pierre Robin sequence
J. Liu, Y. Chen, F. Li, W. Wu, J. Hao, D. Luo, H. Wang Department of Oral and Maxillofacial Surgery, Stomatological Centre, Guangzhou Women and Children’s Medical Centre, Guangzhou, China
J. Liu, Y. Chen, F. Li, W. Wu, J. Hao, D. Luo, H. Wang: Condylar positions before and after bilateral mandibular distraction osteogenesis in children with Pierre Robin sequence. Int. J. Oral Maxillofac. Surg. 2017; xxx: xxx–xxx. ã 2017 Published by Elsevier Ltd on behalf of International Association of Oral and Maxillofacial Surgeons. Abstract. This study aimed to analyze the changes in mandibular morphology after bilateral mandibular distraction osteogenesis (BMDO) in children with Pierre Robin sequence. The positions of the condyles were analyzed in reconstructed threedimensional craniomaxillofacial images obtained for 18 children before and 8–12 weeks after BMDO. Differences between pre- and postoperative parameters were assessed using paired t-tests. After surgery, a significant decrease in superior joint space was detected (P < 0.05), but no change in anterior joint space or posterior joint space was observed. The ratio of the distance between gonia and distance between condylion points (GoL–GoR/CoL–CoR) (P < 0.001) and the distances between the condyle and midsagittal plane (P < 0.001) increased after surgery, while the condylar horizontal angle decreased (P < 0.05). No change in condylar vertical angle was noted. After BMDO, the condyle displayed an outward and upward shift, as well as outward rotation along the proximal segment. The mandible body exhibited forward movement with a more significant opening range. These changes were consistent with the extent of the newly formed bone tissue and the improvement in coordination and appearance of the children’s facial structures. The long-term effects of changes in condylar position on the development of the maxillofacial structures needs to be studied further.
Pierre Robin sequence (PRS) is a rare congenital mandibular abnormality with a reported prevalence ranging between 1/8500 and 1/20,0001. PRS is character0901-5027/000001+07
ized by micrognathia and glossoptosis, with or without cleft palate. The deformities may result in airway obstruction in the neonate, often accompanied by cyanosis
Key words: Pierre Robin sequence; condyle; joint space; bilateral mandibular distraction osteogenesis. Accepted for publication
and retraction of the intercostal space and upper fossa during inspiration. There may be serious clinical consequences for children with multiple PRS malforma-
ã 2017 Published by Elsevier Ltd on behalf of International Association of Oral and Maxillofacial Surgeons.
Please cite this article in press as: Liu J, et al. Condylar positions before and after bilateral mandibular distraction osteogenesis in children with Pierre Robin sequence, Int J Oral Maxillofac Surg (2017), http://dx.doi.org/10.1016/j.ijom.2017.06.019
YIJOM-3735; No of Pages 7
2
Liu et al.
tions, and the mortality rate is estimated to be up to 26%. Also the movement of the epiglottis may be restricted in children with PRS, resulting in chronic malnutrition1. Prone positioning is the first-line noninvasive management of PRS. In the case of persistent airway obstruction, a surgical intervention is required, such as tongue– lip adhesion, tracheotomy, or mandibular distraction osteogenesis (MDO)2. Over the last two decades, distraction osteogenesis has been tested for the correction of temporomandibular joint (TMJ) deformities in animal models as well as in the clinical setting3,4. Bilateral mandibular distraction osteogenesis (BMDO) improves glossoptosis by extending the mandible, thus clearing the airway. This has become the primary choice for the treatment of patients with severe mandibular retrognathia5. It is generally suggested that BMDO is performed at an early stage to improve breathing and nutrition in a timely manner, and therefore to improve quality of life. In BMDO treatment, truncation and facilitated forward movement of the mandible bone segment may cause a shift in position of the teeth, jaws, skull, and/or facial structures. Changes in mandibular morphology and position may affect the fine anatomical structures and function of the TMJ6. Furthermore, the bone composition of infants is more flexible and will adapt during reconstruction of the facial structures. Therefore significant changes in the relative positions of the temporomandibular articulation and mandible may occur during the postoperative period after BMDO treatment. Most perioperative studies have concentrated on changes in the mandible structure from the pathological perspective, with little attention paid to changes in the intact mandible morphology and position during the developmental stages after BMDO, especially the long-term impact on craniofacial development. In this study, the facial structures of patients before and after BMDO treatment were analyzed using reconstructed three-dimensional (3D) craniofacial computed tomography (CT) images. The mandibular morphology was evaluated with quantitative parameters reflecting the relative positions of the condyles. The potential impact of BMDO on the development of the mandibular structures is discussed.
and Children’s Medical Centre. Consecutive patients who underwent BMDO for the treatment of PRS in the Department of Oral and Maxillofacial Surgery of Guangzhou Women and Children’s Medical Centre from May 2013 to October 2015 were included. PRS was diagnosed according to the following criteria: (1) micrognathia and glossoptosis with breathing/swallowing difficulties, defined as the need to maintain a lateral or prone position, or the requirement of assisted mechanical ventilation for respiration, and/or need for tube feeding; (2) reconstructed 3D maxillofacial and laryngeal airway CT images confirming significant tongue falling and upper airway stenosis, with the narrowest position detected between the rear end of the tongue and the hyoid bone. Patients were included in the study if they fulfilled the necessary eligibility criteria, as outlined below.
Eligibility criteria
The following inclusion criteria were applied: confirmed diagnosis of PRS; no previous surgical treatment such as tongue–lip adhesion; preoperative examination showing a normal bilateral TMJ structure with a normal degree of mouth opening; patient able to tolerate surgery under general anaesthesia; the availability of long-term follow-up records (minimum 2 years). Exclusion criteria were the presence of any other severe congenital deformity, metabolic disease, chromosomal disorder,
or dystonia, or the presence of a breathing or eating disorder of unknown cause not directly related to PRS.
Surgical procedure
All patients underwent BMDO under general anaesthesia. A parallel incision was made about 1.5 cm from the inferior border of the mandible close to the mandibular angle. The osteotomy line was designed according to the preoperative 3D CT findings. A ‘walking-stick’ shaped osteotomy line passing through the mandibular angle was utilized to avoid the tooth bud and condylar neck. After a rest period of 48–72 h, mandibular distraction was performed at a speed of 1.2 mm/day. The positioning of the distractors is shown in Fig. 1. Distraction was performed until the upper and lower jaws were symmetrically aligned or a slight underbite was achieved. The maximum traction distance was limited to 1.5 cm. Imaging and analysis of the 3D craniomaxillofacial structures
Three-dimensional maxillofacial CT was performed before and at 8–12 weeks after surgery using a Philips Brilliance CT64 scanner with settings of 120 kV, 130 mA, and 0.9-mm layer thickness. Structure reconstruction was then accomplished using Mimics version 10.0 software (Materialise, NV, Leuven, Belgium) to acquire coronal, sagittal, and axial views.
Methods Setting and patients
This retrospective study was approved by the Ethics Committee of Guangzhou Women
Fig. 1. Positioning of the distractors in this study.
Please cite this article in press as: Liu J, et al. Condylar positions before and after bilateral mandibular distraction osteogenesis in children with Pierre Robin sequence, Int J Oral Maxillofac Surg (2017), http://dx.doi.org/10.1016/j.ijom.2017.06.019
YIJOM-3735; No of Pages 7
Condylar positions before and after BMDO in PRS For the analysis of the craniomaxillofacial structures, morphological parameters were measured, including spatial distances and ratios and relative positions (angles) between anatomical structures, as described below. The superior joint space (SS), anterior joint space (AS), and posterior joint space (PS) were measured as reported previous-
ly7: line ‘a’ was drawn perpendicular to the horizontal plane through the top of the condyle; line ‘b’, which was at 45 degrees to the horizontal plane, was drawn through the narrowest position of the anterior joint space; line ‘c’ was drawn perpendicular to line ‘b’ through the intersection of ‘a’ and ‘b’. The segment lengths of lines ‘a’, ‘b’, and ‘c’, which were located in the joint
3
space, were measured as SS, AS, and PS, respectively, as shown in Fig. 2A. The condylar horizontal angle (a) was measured on the axial image. The angle between the horizontal plane and a line drawn through the inside and outside poles along the long axis was measured as the condylar horizontal angle (a), as shown in Fig. 2B.
Fig. 2. Measurement of the morphological parameters of the craniomaxillofacial structures. (A) Joint spaces: line ‘a’ was drawn perpendicular to the horizontal plane through the top of the condyle; line ‘b’, which was at 45 degrees to the horizontal plane, was drawn through the narrowest position of the anterior joint space; line ‘c’ was drawn perpendicular to line ‘b’ through the intersection of ‘a’ and ‘b’. The segment lengths of lines ‘a’, ‘b’, and ‘c’, which were located in the joint space, were measured as SS, AS, and PS, respectively. (B) Condylar horizontal angle (a): the angle was measured on the axial image; this was the angle between the horizontal plane and a line drawn through the inside and outside poles along the long axis of the condyle. (C) Condylar vertical angle (b): the angle was measured on the coronal image; this was the angle between the sagittal midline and a line drawn through the inside and outside poles along the long axis of the condyle. (D) Distance between the condyle and midsagittal plane (r): this distance was measured on axial images as the distance between the outside pole of the condyle and the midsagittal plane. (E) GoLGoR/CoL-CoR ratio: the distance between gonia on the two sides (GoL-GoR) and the distance between condylion points on the two sides (CoLCoR) were measured; the ratio between these distances was used to evaluate the degree of opening of the mandibular arch relative to positioning between the condyle and mandibular body.
Please cite this article in press as: Liu J, et al. Condylar positions before and after bilateral mandibular distraction osteogenesis in children with Pierre Robin sequence, Int J Oral Maxillofac Surg (2017), http://dx.doi.org/10.1016/j.ijom.2017.06.019
YIJOM-3735; No of Pages 7
4
Liu et al.
Table 1. Characteristics of the study subjects and mandible extension results.
Patient ID number
Sex
Age (days)
Weight (kg)
Requirement for assisted mechanical ventilation
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
M F M F M F M F M M F M F M F F F M
69 107 244 110 52 24 31 50 153 213 160 48 93 213 17 42 17 87
3.1 3.5 8.3 3.2 4.4 2.9 3.2 3.4 4.6 6.4 4.5 4.4 4.1 6 3.1 2.6 3 5
N N N N N N Y N N N N N N Y N N N N
Requirement for auxiliary feeding tube
Postoperative extension of the mandible (left/right) (mm)
Y N N Y Y Y Y N Y N N N N Y Y Y Y Y
12/12 12/12 10/10 8/8 13.6/18.4 15/20 11.5/10 1.5/15 15/15 13.5/10 11.5/2 8/1 12.5/12.5 13.5/3.5 11.5/10 15/12.5 13.5/15 12.5/8.5
F, female; M, male; Y, yes; N, no.
The condylar vertical angle (b) was measured on the coronal image. The angle between the sagittal midline and a line drawn through the inside and outside poles along the long axis of the condyle was measured as the condylar vertical angle (b), as shown in Fig. 2C. The distance between the condyle and midsagittal plane (r) was measured on the axial image. This was the distance between the outside pole of the condyle and the midsagittal plane, as shown in Fig. 2D. The distances between the gonia on the two sides (GoL–GoR) and the distance between the condylion points on the two sides (CoL–CoR) were measured, as shown in Fig. 2E. The ratio between these two distances (GoL–GoR/CoL–CoR ratio) was used to evaluate the degree of opening of the mandibular arch relative to positioning between the condyle and mandibular body.
Statistical analysis
Parameters measured were expressed as the mean standard deviation. Comparisons between the pre- and postoperative data were performed using the paired ttest. A P-value of 0.05), indicating that there was no significant movement in the anterior or posterior direction of the proximal segment of the mandible. Significant increases in r values were observed after surgery (P < 0.001), indicating an outward movement of the condyles. The GoL–GoR/CoL–CoR ratio was increased postoperatively compared to the value before surgery (P < 0.001), indicating an increase in mandibular opening and a widening of the mandibular arch. The angle a was increased on both sides (both P < 0.05) after the completion of distraction, while no significant change in angle
Table 2. Comparison of morphological parameters before and after surgery. N = 18
Preoperative
Postoperative
SS-L (mm)* SS-R (mm)* AS-L (mm) AS-R (mm) PS-L (mm) PS-R (mm) a-L ( )* a-R ( )* b-L ( ) b-R ( ) r-L (mm)* r-R (mm)* GoL–GoR/CoL–CoR*
2.12 0.43 2.20 0.57 1.90 0.46 1.92 0.41 3.35 0.78 3.15 0.73 24.94 6.60 26.07 8.28 78.12 8.36 76.75 10.03 34.95 2.63 34.88 2.50 0.75 0.05
1.90 0.40 1.91 0.38 2.00 0.52 2.04 0.47 3.19 0.71 3.33 0.88 20.46 8.97 21.04 9.01 78.03 5.96 76.61 7.26 39.40 2.46 40.09 3.01 0.77 0.06
t
P-value 2.779 2.567 0.845 0.888 0.681 0.780 3.324 3.582 0.043 0.050 5.972 8.744 4.986
L, left; R, right; SS, superior joint space; AS, anterior joint space; PS, posterior joint space; a, condylar horizontal angle; angle; r, distance between condyle and midsagittal plane; Go, gonion; Co, condylion. * Statistically significant difference detected between pre- and postoperative measurements.
0.004 0.009 0.409 0.387 0.505 0.446 0.020 0.014 0.966 0.961
